Which pesticide is derived from plants?

Rotenone is derived from the roots of various plants, particularly those belonging to the Leguminosae family, such as the jicama plant and certain types of legumes. It has been used as a natural pesticide because of its ability to effectively target specific pests, particularly aquatic insects and fish.

This natural origin is significant because it distinguishes rotenone from the other substances listed in the choices. Arsenic and boron are elements found in nature but are not plant-derived pesticides; they are minerals that can have toxic effects. Chlorine is a chemical element often used in sanitation and disinfection processes, but it doesn't come from plants. This highlights the unique characteristic of rotenone as a plant-based pesticide, making it the best answer to the question.